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Contact dermatitis is an inflammatory eczematous skin disease. Contact dermatitis is a type of inflammation of the skin. It results from either exposure to allergens (allergic contact dermatitis) or irritants (irritant contact dermatitis). Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight. Diagnosis of allergic contact dermatitis can often be supported by patch testing.[rx]It is caused by chemicals or metal ions that exert toxic effects without inducing a T-cell response (contact irritants) or by small reactive chemicals that modify proteins and induce innate and adaptive immune responses (contact allergens).[rx][rx][rx][rx]

Pathophysiology of Contact Dermatitis

The pathophysiology of allergic contact dermatitis (ACD) begins with the contact of the allergen to the skin. The allergen penetrates that stratum corneum and is taken up by Langerhans cells.[rx] The antigens are subsequently processed by these cells and displayed on their surface. As part of the skin’s normal immunity, Langerhans cells migrate towards regional lymph nodes. The antigens taken up by the Langerhans cells come in contact with the adjacent T-lymphocytes.[rx] Because of the process of clonal expansion as well as cytokine-induced proliferation, antigen-specific T lymphocytes are created. These lymphocytes may then traverse through the blood and into the epidermis. This process collectively is known as the sensitization phase of allergic contact dermatitis.[rx] The elicitation phase is what occurs after reexposure to the antigen takes place. The Langerhans cells containing the antigen interacts with the antigen-specific T-lymphocytes for that antigen which triggers a cytokine-induced proliferation process.[rx] This, in turn, creates a localized inflammatory response.

Types of Contact Dermatitis

There are three types of contact dermatitis: irritant contact dermatitis; allergic contact dermatitis; and photocontact dermatitis. Photocontact dermatitis is divided into two categories: phototoxic and photoallergic.

Irritant contact dermatitis

Irritant contact dermatitis (ICD) can be divided into forms caused by chemical irritants, and those caused by physical irritants. Common chemical irritants implicated include:

Allergic contact dermatitis (ACD) is accepted to be the most prevalent form of immunotoxicity found in humans, and is a common occupational and environmental health problem.[rx]

By its allergic nature – this form of contact dermatitis is a hypersensitive reaction that is atypical within the population. The mechanisms by which this reaction occurs are complex, with many levels of fine control. Their immunology centres on the interaction of immunoregulatory cytokines and discrete subpopulations of T lymphocytes.

Allergens include nickel – gold, Balsam of Peru (Myroxylon pereirae), chromium, and the oily coating from plants of the genus Toxicodendron, such as poison ivy, poison oak, and poison sumac.

Photocontact dermatitis

Sometimes termed “photoaggravated”,[rx] and divided into two categories, phototoxic and photoallergic, PCD is the eczematous condition which is triggered by an interaction between an otherwise unharmful or less harmful substance on the skin and ultraviolet light (320–400 nm UVA) (ESCD 2006), therefore manifesting itself only in regions where the sufferer has been exposed to such rays.

Both irritant contact dermatitis and allergic contact dermatitis can present with three morphological patterns.

The alkyl resorcinols in Grevillea banksii and Grevillea ‘Robyn Gordon’ are responsible for contact dermatitis.[rx] Bilobol, another alkyl resorcinol found in Ginkgo biloba fruits, is also a strong skin irritant.[rx]

Symptoms of Contact Dermatitis

Symptoms of both forms include the following:

Red rash. This is the usual reaction. The rash appears immediately in irritant contact dermatitis; in allergic contact dermatitis, the rash sometimes does not appear until 24–72 hours after exposure to the allergen.

Blisters or wheals. Blisters, wheals (welts), and urticaria (hives) often form in a pattern where skin was directly exposed to the allergen or irritant.

Itchy, burning skin. Irritant contact dermatitis tends to be more painful than itchy, while allergic contact dermatitis often itches.

a red rash, often without clearly defined edges,

Itchy skin (often intense)

Rash (skin red, swollen, and hot)

Excessively dry skin

Burning

Stinging

Hives (round welts on the skin that itch intensely)

Fluid-filled blisters

Oozing blisters that leave crusts and scales

swelling,

itching, and

dry skin.

Diagnosis of Contact Dermatitis

History and Physical

Symptoms of irritant contact dermatitis may include burning, itching, stinging, soreness, and pain, particularly at the beginning of the clinical course, while pruritus is more common in allergic contact dermatitis. Patients with a history are at increased risk for developing nonspecific hand dermatitis and irritant contact dermatitis.

Distinguishing Features of Irritant and Allergic Contact Dermatitis

Feature

Irritant Contact Dermatitis

Allergic Contact Dermatitis

Pathogenesis

Direct cytotoxic effect

T cell-mediated immune reaction

Affected individuals

Everyone

A minority of individuals

Onset

Immediate (chemical burns)

12-48 h in previously sensitized individuals

After repeated exposure to weak irritants

Signs

Subacute or chronic eczema with desquamation, fissures

Acute to subacute eczema with vesiculation

Symptoms

Pain or burning sensation

Pruritus

Concentration of contactant

High

Low

Investigation

None

Patch or prick tests

Testing for allergens

The best way to test for a reaction to allergens is by patch testing. During a patch test, tiny amounts of known allergens are applied to your skin. The substances are attached to your back using a special kind of non-allergic tape. They may sometimes be attached to the upper arms. After two days, the patches are removed and your skin assessed to check if there has been any reaction.

Your skin will usually be examined again after a further two days, as most allergic contact dermatitis reactions take this long to develop.

Testing for irritants

It’s very difficult to test whether specific products irritate your skin, because testing for these is very unreliable.In some cases, a repeated open application test (ROAT) is useful, particularly to assess cosmetics. A ROAT involves reapplying the substance onto the same area of skin twice a day for 5 to 10 days, to see how your skin reacts.

Treatment of Contact Dermatitis

Self-care

If blistering develops – cold moist compresses[rx] applied for 30 minutes, 3 times a day can offer relief.

In hand dermatitis – avoiding excessive hand washing and using non-irritating moisturizers is recommended. Choose mild soaps, moisturizers, and detergents without dyes or perfumes. Wear gloves to protect your hands and other body parts from exposure if contact with these chemicals is unavoidable, however be aware that you can become allergic to chemicals in the gloves as well.

In foot dermatitis – the use of barrier socks may be helpful.

Wash skin immediately – after contact with an allergen to limit the spread and severity of the reaction such as after known contact with a plant allergen (poison ivy).

Immediately after exposure to a known allergen or irritant – wash with soap and cool water to remove or inactivate most of the offending substance.

For mild cases that cover a relatively small area – hydrocortisone cream in nonprescription strength may be sufficient.

Weak acid solutions (lemon juice, vinegar) – can be used to counteract the effects of dermatitis contracted by exposure to basic irritants.

A barrier cream – such as those containing zinc oxide (e.g., Desitin, etc.), may help protect the skin and retain moisture.

Medical care

If the rash does not improve or continues to spread after 2–3 of days of self-care, or if the itching and/or pain is severe, the patient should contact a dermatologist or other physician. Medical treatment usually consists of lotions, creams, or oral medications.

Corticosteroids – A corticosteroid medication like hydrocortisone may be prescribed to combat inflammation in a localized area. It may be applied to the skin as a cream or ointment. If the reaction covers a relatively large portion of the skin or is severe, a corticosteroid in pill or injection form may be prescribed.

In severe cases – a stronger medicine like halobetasol may be prescribed by a dermatologist.

Friction – should be avoided as well as the use of soaps, perfumes, and dyes. Emollients are used for hydrating the skin. Tacrolimus ointment and pimecrolimus cream are immunomodulating drugs that inhibit calcineurin and are helpful in allergic contact dermatitis.

Topical Immunomodulators – Topical calcineurin inhibitors (pimecrolimus, tacrolimus) are anti-inflammatory agents that may provide another option in patients with ACD or ICD. However, they are not FDA approved for CD. They do not cause skin thinning, which is beneficial for the treatment of patients with facial dermatitis and dermatitis in other sensitive areas (bending areas, genitals). The most common adverse effects encountered are burning and itch at the application site.

Topical Antibiotics – These creams or ointments are sometimes used if there are open fissures and evidence of a secondary bacterial infection. However over-the-counter topical antibiotics are frequent causes of CD and should be used under the recommendation of your allergist / immunologist.

Topical Steroids – Topical steroids are anti-inflammatory medications. They help to get the rash under control more quickly and are usually applied 1-2 times a day. Topical steroids come in different formulations and strengths. Milder topical steroids such as hydrocortisone can be purchased over the counter. If the rash is not improving after 7 days or getting worse, you should consult your physician. A more potent topical steroid may be required, but should be used sparingly in sensitive areas such as the face, underarms and groin as they can thin the skin and cause stretch marks.

Unfortunately – recurrence is common and people with no identifiable cause have a poor quality of life.[rx] A nurse educator specializing in dermatology and dermatology should work together to assist in patient education, particularly for challenging cases.

Avoiding the noxa – Contact dermatitis is triggered by exogenous toxins in the vast majority of cases. The most important therapeutic approach, therefore, is to cease causal exposure — no form of symptomatic treatment can substitute for this approach. Attempts to induce tolerance to contact allergens by means of immunotherapy have been hitherto unsuccessful [rx, rx].

Calcineurin antagonists – In Germany, Austria, and Switzerland, calcineurin antagonists are only approved for the treatment of atopical dermatitis. They are less effective than strong corticosteroids in manifest contact dermatitis [rx, rx, rx]. However, if long-term use is indicated, topical calcineurin antagonists may be beneficial in contact dermatitis compared to corticosteroids, particularly in sensitive areas of the skin (e. g., face, intertriginous areas), since they carry no atrophy risk [rx]. With regard to safety, the reader is referred to the AWMF guidelines of the DDG on topical calcineurin antagonists and neurodermatitis [rx, rx].

Ultraviolet therapy – Short-wave ultraviolet light (UVB) and PUVA (psoralen plus UV-A) are effective in chronic dermatitis, most notably in hand dermatitis [rx, rx, rx, rx]. In some forms of hand dermatitis, topical application of psoralens is advisable in the context of PUVA therapy in order to intensify the therapeutic effect. It appears possible to achieve a certain degree of “protective hardening” using UVB [rx]. Positive data are also available on the use of UVA1 and narrow-band UVB, particularly in hand dermatitis [rx, rx, rx].

Other external agents – Due to its antiphlogistic and antiproliferative effects, the use of coal tar as a follow-up treatment is still reasonable today in cases where other external agents are ineffective or declined by the patient. There is no evidence to support the fear that local treatment with coal tar is carcinogenic [rx,rx, rx,rx].

Phototherapy – Your allergist / immunologist may refer you to a dermatologist for light therapy if the rash is not responding to the above therapy.

Basic therapy and skin protection

Follow-up treatment with basic moisturizing agents to promote skin barrier regeneration and protect against recurrence, combined with the use of skin protection creams, is beneficial when individually tailored to skin status and skin exposure [rx, rx, rx]. On the other hand, preparations containing unsuitable levels of water and fat or allergenic components may delay the resolution of dermatitis or even intensify the effect of substances harmful to the skin [rx]. Although skin protection training is beneficial in the case of hazardous occupational exposure [rx], the effectiveness of skin protection creams alone under working conditions has not be unequivocally proven [rx]. Complete restoration of barrier function is not expected until several weeks after the clinical resolution of contact dermatitis. However, the beneficial effect of moisturizers is measurable [rx].

Prevention of Contact Dermatitis

General prevention steps include the following

Avoid irritants and allergens. Try to identify and avoid substances that irritate your skin or cause an allergic reaction.

Wash your skin. You might be able to remove most of the rash-causing substance if you wash your skin right away after coming into contact with it. Use a mild, fragrance-free soap and warm water. Rinse completely. Also wash any clothing or other items that may have come into contact with a plant allergen, such as poison ivy.

Cleaning your skin – if you come into contact with an allergen or irritant, rinse the affected skin with warm water and an emollient as soon as possible

Using gloves to protect your hands – but take them off every now and again, as sweating can make any symptoms worse; you may find it useful to wear cotton gloves underneath rubber gloves if the rubber also irritates you

Changing products that irritate your skin – check the ingredients on make-up or soap to make sure it does not contain any irritants or allergens; in some cases, you may need to contact the manufacturer or check online to get this information

Applying emollients frequently and in large amounts – these keep your skin hydrated and help protect it from allergens and irritants; you could also use emollient soap substitutes rather than regular bar or liquid soaps, which can dry out your skin

Wear protective clothing or gloves. Face masks, goggles, gloves and other protective items can shield you from irritating substances, including household cleansers.

Apply an iron-on patch to cover metal fasteners next to your skin. This can help you avoid a reaction to jean snaps, for example.

Apply a barrier cream or gel. These products can provide a protective layer for your skin. For example, an over-the-counter skin cream containing bentoquatam (IvyBlock) may prevent or lessen your skin’s reaction to poison ivy.

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